A typical reciprocating compressor will have a valve plate with one, or more, suction ports and discharge ports formed therein. Normally the Suction and discharge valves will be of the same general type. Each valve would be normally closed and would open due to a pressure differential across the valve in the direction of opening. Since suction valves open into the compression chamber/cylinder they generally do not have valve backers in order to minimize the clearance volume and thus deflection of the valve is not physically limited. When a suction valve opens, the valve lip(s) engage recess(es) in the housing structure defining the piston cylinder after a small amount of opening movement with further opening being due to flexure of the valve away from the valve seat and into the cylinder.
The resilience of the suction valves and adherence of the valve to the valve seat due to an oil film (“stiction”) resists the opening of the suction valve. The opening movement of the suction valve before the tip(s) engage the recess(es) would only permit a restricted flow into the cylinder. So, the valve tip slams into the recess and flexes into the cylinder for every cycle. The greatest degree of flexure occurs, nominally, at the mid-point of the valve between the tip support and the pin support. Because the valve tips are located near the suction ports and because the valve tips are in a nominal line contact with the housing structure, the valve tips tend to be stressed which can result in valve failure by permitting the valve to be drawn into the cylinder.